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1-1: To understand the universe, astronomers use laws of physics to construct testable theories and models
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UniverseTenth Edition
Chapter 1Astronomy and the
Universe
Roger Freedman • Robert Geller • William Kaufmann III
By reading this chapter, you will learn
• 1-1: What distinguishes the methods of science from other human activities
• 1-2: How exploring other planets provides insight into the origins of the solar system and the nature of our Earth
• 1-3: Stars have a life cycle—they form, evolve over millions or billions of years, and die
• 1-4: Stars are grouped into galaxies, which are found throughout the universe
• 1-5: How astronomers measure the positions and sizes of celestial objects
• 1-6: How to express very large or very small numbers in convenient notation
• 1-7: Why astronomers use different units to measure distances in space
• 1-8: What astronomy can tell us about our place in the universe
1-1: To understand the universe, astronomers use laws of physics to construct testable
theories and models
Our Star, the Sun
Planets Orbiting the Sun
A Telescope in Space
The Sun and Planets to Scale
1-1: By exploring the planets, astronomers uncover clues about the formation of the solar
system
Stars like Grains of Sand
1-3: By studying stars and nebulae, astronomers discover how stars are born, grow
old and die
A Thermonuclear Explosion
The Orion Nebula – Birthplace of Stars
The Crab Nebula – Wreckage of an Exploded Star
A Galaxy
1-4: By observing galaxies, astronomers learn about the origin and fate of the universe
A Quasar
1-5: Astronomers use angles to denote the positions and apparent sizes of objects in the
sky
Estimating Angles with Your Hand
The Small Angle Formula
Examples of Powers-of-Ten Notation
1-6: Powers-of-ten notation is a useful shorthand system for writing numbers
1-7: Astronomical distances are often
measured in astronomical units, light-years or
parsecs
A Hurricane Seen from Space
1-8: Astronomy is an adventure of the human spirit
Sizes in the Universe
Key Ideas• Astronomy, Science, and the Nature of the Universe: The universe is
comprehensible. The scientific method is a procedure for formulating hypotheses about the universe. Hypotheses are tested by observation or experimentation in order to build consistent models or theories that accurately describe phenomena in nature.
• Observations of the heavens have helped scientists discover some of the fundamental laws of physics. The laws of physics are in turn used by astronomers to interpret their observations.
• The Solar System: Exploration of the planets provides information about the evolution of the solar system as well as about the history and resources of Earth.
• Stars and Nebulae: Studying the stars and nebulae helps us learn about the history and origin of the Sun and the solar system
Key Ideas• Galaxies: Observations of galaxies tell us about the origin and history of the
universe.• Angular Measure: Astronomers use angles to denote the positions and
sizes of objects in the sky. The size of an angle is measured in degrees arcminutes and arcseconds.
• Powers-of-Ten Notation: A convenient shorthand system for writing numbers. It allows very large and very small numbers to be expressed in a compact form.
• Units of Distance: Astronomers use a variety of distance units. These include the astronomical unit (the average distance from the Earth to the Sun), the light-year (the distance that light travels in a year), and the parsec.
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